Proposition 2 (Maximum acyclic induced subgraph (MAIS) bound, [1]}) 
Consider a non-secure index coding problem \((W_i|A_i,\emptyset ),i\in [m]\) .
The (non-secure) symmetric capacity \(C\)  is upper bounded by the MAIS upper bound \(C_{\rm MAIS}\) , which is defined as the reciprocal of the cardinality of the largest acyclic set \(K\subseteq [n]\) .
That is,
\(C\le C_{\rm MAIS}\doteq \max _{K\subseteq [n]:\text{$K$ is acyclic}}\frac{1}{|K|}.\) 

